The current flowing across a surface of liquid hydrogen has been measu
red as a function of the temperature and the polarity and magnitude of
the applied voltage. Positive charges do not penetrate into the vapor
from the liquid to any significant extent. Below 17 K, the temperatur
e dependence of the current of negative charges can be described by an
exponential function with an activation energy of 350+/-70 K. The exp
erimental results imply that two types of negative charges, differing
in structure, exist in the liquid hydrogen: electron bubbles and clust
ers, which, like positively charged ion clusters, accumulate below the
surface of the liquid. (C) 1994 American Institute of Physics.